Download An Anatomical Variation in the Formation of the Inferior Root of Ansa

DOI: 10.7860/JCDR/2013/5601.3513
Case Report
Anatomy Section
An Anatomical Variation in the
Formation of the Inferior Root of
Ansa Cervicalis
Srinivasa Rao Sirasanagandla1, Satheesha Nayak B2, Naveen Kumar3,
Jyothsna Patil4, Swamy Ravindra S5
ABSTRACT
During regular dissections, we observed an unusual organization of the inferior root of Ansa Cervicalis (AC). The superior root of ansa arose
normally from the hypoglossal nerve. The ventral ramus of the C2 spinal nerve divided into two branches. One of its branches joined the
superior root independently to form a loop at a higher level. Another branch ran along the vagus nerve, joined with the ventral ramus of C3
spinal nerve, finally connected with the superior root and formed the second loop at a lower level. No variation was found in formation of
superior root. Knowledge on the possible deviations in the formation of these roots is clinically important, to prevent iatrogenic injuries in
surgical procedures such as thyroplasties, arytenoids adductions, and Teflon injections.
Key words: Ansa cervicalis, Anastomosis, Inferior root, Recurrent laryngeal nerve, Superior root
Case report
During regular dissection classes which were held for the medical
students, we came across a variation in the inferior root of AC, on
the left side of the neck of an adult male cadaver. As usual, the fibers
of C1 joined the Hypoglossal Nerve (HN) and after a short course,
separated from it and formed the superior root of AC. The common
form of formation of inferior root of the AC, which is formed by the
union fibres of C2 and C3, was absent. The fibers of the C2 divided
into two branches (C2a and C2b) [Table/Fig-1]. One of its branches
(C2a) joined the superior root independently to form a loop at a
higher level and it was situated superficial to the Internal Jugular Vein
(IJV). Another branch (C2b) ran along the vagus nerve, joined with
the fibres of C3, finally connected with the superior root and formed
the second loop at a lower level. The second loop was found to be
present deep in the IJV. Superior belly of omohyoid received the
nerve supply from the superior root. The other infrahyoid muscles
were supplied by a common branch which arose from the second
loop [Table/Fig-1].
[Table/Fig-1]: Dissection of anterior triangle of left side neck showing
the formation of superior and inferior root of ansa cervicalis. (C2a & C2b:
two branches of ventral ramus of second spinal nerve; C3: ventral ramus
of third spinal nerve; FL; first loop; SL: second loop; HN: hypoglossal
nerve; VN: vagus nerve; NT: nerve to thyrohyoid; CB: common branch
to infrahyoid muscles; NS: nerve to superior belly of omohyoid; CCA:
common carotid artery; IJV: internal jugular vein; SM: sternomastoid
muscle; SBO: superior belly of omohyoid muscle)
Journal of Clinical and Diagnostic Research. 2013 Oct, Vol-7(10): 2319-2320
Discussion
The Ansa Cervicalis (AC) is a nerve loop that is formed by the
union of its superior and inferior roots. As various cervical roots are
involved in the inferior root formation, it frequently shows variations
as compared to superior root [1]. An inferior root may be absent [2]
or rarely, it may be formed by the rootlets of spinal accessory nerve
and cervical plexus to sternomastoid muscle [3]. Knowledge on the
anatomical variations of the AC is important, as it is frequently used
to innervate the paralyzed muscles of the larynx [4].In a cadaveric
study by Poviraev and Chernikov, the classical inferior root formation
by ventral rami of C2 and C3 was observed in 74% of the cases.
In their study, inferior root formation was contributed by C3 in 5%
of cases, C2, C3 and C4 in 14% of cases C2 in 4% of cases and
by C1, C2 and C3 in 2% of the cases [5]. Caliot and Dumont have
observed the formation of inferior root by C3 in 80% of cases and
by C2 in 36% of the cases [6]. In another study which was done by
Loukas et al., inferior root was found to be derived from the ventral
rami of C2 and C3 in 38% cases, from C2, C3 and C4 in 10%
cases, from C3 in 40% cases and from C2 in 12% of the cases [7].
Absence of inferior root was rarely observed. Earlier, it was reported
with a frequency of up to 3% [2]. In another study, the inferior root
was noted to be absent in 10.5% of the cases on the right side and
in 18.4% of the cases on the left side [8]. In the present case, in
addition to the usual loop, an extra loop was observed at a higher
level, which was formed by one of the branches of C2 after joining
the superior root.
In relation to the IJV, the course of the inferior root has been
described to have three patterns: medial, lateral, and mixed types
[6], [9]. If the ansa is situated deep in the internal jugular vein, then it
is described as medial type, and when it lies superficial to the same
vein, it is described as lateral type. Rarely, does the inferior root
divide into branches that join the superior root independently [9]. In
such cases, some of the branches may lie superficial to the internal
jugular vein, with the rest passing deep into this vein, resulting in a
mixed type. In a study which was conducted by Mwachaka et al.,
81.5% of the inferior roots were found to be of the lateral type, while
19.5% were found to be of the medial type [8]. In the present case,
we observed the mixed type, where one of the branch of C2 (C2a)
was situated superficial to the IJV and another branch (C2b) was
found to be present deep in the IJV.
Phonation malfunctions which were caused by a loss of laryngeal
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Srinivasa Rao Sirasanagandla et al., Unusual Inferior Root of Ansa Cervicalis
muscle innervations were successfully retrieved by creating an
anastomosis between the AC and the recurrent laryngeal nerve
[10].
Conclusion
Awareness on variations of AC is clinically important, to prevent
injuries to the common carotid artery and IJV. The knowledge on
unusual organization of inferior root of AC is also important, to
prevent iatrogenic injuries to the AC.
References
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[3] Khaki AA, Shokouhi G, Shoja MM, Farahani RM, Zarrintan S, Khaki A, et al. Ansa
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cervicalis. Rev Laryngol Otol Rhinol (Bord). 1983;104:441–44.
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cervicalis revisited. Folia Morphol. 2007;66:120–25.
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ansa cervicalis. Folia Morphol. 2010;69:160–63.
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Anatomical Science International. 2008;83:31–44.
Brondbo K, Jacobsen E, Gjellan M, Refsum H. Recurrent laryngeal nerve - ansa
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PARTICULARS OF CONTRIBUTORS:
1. Lecturer, Department of Anatomy, Melaka Manipal Medical College (Manipal Campus), Manipal University,
Madhav Nagar, Manipal, Karnataka – 576104, India.
2. Professor and Head, Department of Anatomy, Melaka Manipal Medical College (Manipal Campus),
Manipal University, Madhav Nagar, Manipal, Karnataka – 576104, India.
3. Lecturer, Department of Anatomy, Melaka Manipal Medical College (Manipal Campus),
Manipal University, Madhav Nagar, Manipal, Karnataka – 576104, India.
4. Lecturer, Department of Anatomy, Melaka Manipal Medical College (Manipal Campus),
Manipal University, Madhav Nagar, Manipal, Karnataka – 576104, India.
5. Lecturer, Department of Anatomy, Melaka Manipal Medical College (Manipal Campus),
Manipal University, Madhav Nagar, Manipal, Karnataka – 576104, India.
NAME, ADDRESS, E-MAIL ID OF THE CORRESPONDING AUTHOR:
Dr. Satheesha Nayak B,
Professor and Head, Department of Anatomy, Melaka Manipal Medical College (Manipal Campus)
Manipal University, Madhav Nagar, Manipal, Karnataka – 576104, India.
Phone: +91 9844009059, E-mail: [email protected]
Financial OR OTHER COMPETING INTERESTS: None.
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Date of Submission: Jan 08, 2013
Date of Peer Review: May 15, 2013
Date of Acceptance: Jun 06, 2013
Date of Publishing: Oct 05, 2013
Journal of Clinical and Diagnostic Research. 2013 Oct, Vol-7(10): 2319-2320